"In essence, the stimulus check acts as an advance of your 2020 income tax refund. This means when you prepare your 2020 income tax return, there will be a line to include the section 6428 credit. The credit on your 2020 return is subtracted by any amount received as a stimulus check in 2020. If the amount you received as a stimulus check is less than the credit you are due, the difference will be included as part of your 2020 refund. If you have been overpaid by receiving the stimulus check, however, you will not be required to return any excess amount".
That says if, in the case of divorced or separated (including never married) parents, the other parent got $500 + $600 in 2020 (because he claimed the child on his 2019 return) you also get it in 2021, if you claim the child on your 2020 return. It's a tax loop hole, you both get the money! Be sure the ex doesn't try to claim the child on his 2020 return.
